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Old 6th November 2004, 15:57   #1  |  Link
Sharktooth
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Bug report: Xvid quant 1+trellis is broken!

Look here: http://forum.doom9.org/showthread.php?s=&threadid=84975
I tested the quant 1 behaviour with TRELLIS ENABLED with 1.02, Koepi 1.1beta (first and second build).
In every case there was blocking with some custom matrices.
I'm trying to estabilish what "kind" of matrices does trigger that bug.
For sure EQM V3HR triggers the bug:
http://ebola.gamersrevolt.it/xvid_quant1_bug.avi
http://ebola.gamersrevolt.it/xvid_quant1_bug_2.avi

Disabling Trellis quantization fixes the blocking.

Last edited by Sharktooth; 6th November 2004 at 16:08.
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Old 6th November 2004, 21:31   #2  |  Link
COREiP
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Is this a decoder bug?
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Old 7th November 2004, 19:41   #3  |  Link
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Well, at least it's just when quant 1 is used. Not a show-stopper bug.
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Old 8th November 2004, 10:01   #4  |  Link
*.mp4 guy
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Actually its not just at quant 1... I just reviewed a couple of old test encodes with Didee's sixofnine hvs matrice and I noticed faint flickering dark(er) blocks in all instances. It was much more pronounced on light and or smooth areas like wals, however im not sure if its fixed by disdabling trellis, as its a feature i always use. can someone else confirm that its not just quant 1?
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Old 8th November 2004, 11:10   #5  |  Link
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...and I was hoping we fixed all those stupid overflows in trellis...
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Old 8th November 2004, 14:03   #6  |  Link
Teegedeck
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...nothing like that on my end! You sure it ain't a decoder thang?

No flickering blocks, nor mysterious blocking in my encodes (mostly SixOfNine custom quant, Trellis of course).

@*.mp4 guy: How old are those 'old test encodes'?
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Last edited by Teegedeck; 8th November 2004 at 14:05.
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Old 8th November 2004, 14:25   #7  |  Link
Sharktooth
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It's not a decoder issue (tested with DivX, Xvid, FFDShow, 3ivx decoders). Using the same settings but disabling Trellis fixes the blocking. That means Trellis has still some bugs (overflows as syskin wrote).
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Old 8th November 2004, 15:20   #8  |  Link
Teegedeck
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You only found those glitches in quant=1, didn't you, Sharktooth? As I don't use quant=1 and have never encountered that bug, I assume that what *.mp4 guy discovered there probably doesn't really concern this build?
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Old 8th November 2004, 15:27   #9  |  Link
Sharktooth
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Sorry Teegedek i thought you were talking to me in your previous post.
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Old 9th November 2004, 04:53   #10  |  Link
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The encodes I was refering to were made with the 1.1 beta for vhq on b-frames. Its probably a different bug(b-frame vhq perhaps) but I thought there was a chance the two could be related.
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Old 11th November 2004, 11:12   #11  |  Link
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I did also some quantizer1_test_encodes, but i can't confirm the trellis bug ... i used one of the latest 1.1 builds from celtic_druid (xvid.cvs.head.gcc.p4.2004.10.18.7z) with 6of9_hvs-matrix, anamporph in mkv....

here are the samples:
http://home.arcor.de/evil.bert/Xvid%20Test/

settings: single pass, q1, trellis/no trellis, gmc, vhq 4, vhq for b-frames, b-frames 3/1,5/1, qpel, glosed gov, chroma...
note: teaser.mkv is a two-pass file, targeting by 1024 kb, same settings (trellis enabled)...
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Old 11th November 2004, 12:36   #12  |  Link
yaz
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Quote:
Originally posted by kurt
I did also some quantizer1_test_encodes, but i can't confirm the trellis bug ... i used one of the latest 1.1 builds from celtic_druid (xvid.cvs.head.gcc.p4.2004.10.18.7z)...
the same here with an athlon build and with mpeg, h263 and the (good-old-)vhs series. it seems as if it were a matrix problem ...

just occured ... the same problem came up with mpeg2 encoding when i tested a series of cqm. trellis didn't like some matrices, definitely. (a typical example was the (in)famous notch-matrix from kvcd) iirc, the problematic matrices had quite strange 'profiles'. say, most of them had very steep parts a/o local minima/maxima a/o drops/shifts instead of smooth transients ... just thinking aloud

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Old 11th November 2004, 14:40   #13  |  Link
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A matrix can't be "problematic"... The codec handling of those matrices IS "problematic"...
If the codec chooses the wrong quantizers it's a codec bug, not a matrix problem.
In the xvid case it's a trellis overflow.
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Old 12th November 2004, 12:11   #14  |  Link
yaz
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Quote:
Originally posted by Sharktooth
A matrix can't be "problematic"... The codec handling of those matrices IS "problematic"...
If the codec chooses the wrong quantizers it's a codec bug, not a matrix problem.
In the xvid case it's a trellis overflow.
"if u say so and if it's true i will believe it." sure, i will :-) however ...
if a codec works fine with 10 different matrices but the 11th triggers some trouble i've called that matrix problematic (and i haven't used). now i will call it "problematic" (and i wont use:-). is that ok ? :-)

anyway, i talked about mpeg2 encoding with mencoder, so, there's nothing to do with xvid here. and, maybe, the problem is more general than u prompt. maybe.

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Last edited by yaz; 12th November 2004 at 12:23.
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Old 12th November 2004, 13:14   #15  |  Link
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Oh well, maybe also other codecs have bugs.
what i want to say is a CQM is composed by 2 parts: the intra-matrix and the inter-matrix.
If the coefficients of both matrices are between 8 and 255 there is nothing "problematic" with that CQM.
I used that matrix (EQM V3HR) with other codecs and there were no problems at all.
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Old 16th November 2004, 20:42   #16  |  Link
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I too experienced some blockiness on some encodes.
I don't know if it's CQM-related or Trellis/B-VHQ-related though...
I've done 2 full test encodings of Matrix, with same XviD settings, using EQM_V3LR for one and EQM_V3ULR for the other.

Xvid settings was:

2-pass
AQ/GMC/B-Frames default values
MSP6/VHQ4/B-VHQ/Chroma Motion
Trellis
Respect VBV buffer unchecked

The ULR one showed some blockiness only on scenechanges (I-frames), while LR was perfect.

Just to have another example...

EDIT: the blockiness happens on ALL scenechanges with ULR, so P and B frames after every I-frame are affected by a side-effect, being these based on a bad I-frame...
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Last edited by Ark; 16th November 2004 at 21:32.
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Old 17th November 2004, 03:47   #17  |  Link
Sharktooth
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At what bitrate you encoded the movie?
Did you used some smoothing/denoising filters?
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Old 17th November 2004, 09:27   #18  |  Link
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Quote:
Originally posted by Sharktooth
At what bitrate you encoded the movie?
Did you used some smoothing/denoising filters?
Bitrate is +/- 800kb, I used:

mpeg2source("matrix.d2v")
crop(8,80,704,416)
temporalsoften(1,2,4,15,2)
simpleresize(640,272)
undot()
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Old 17th November 2004, 13:04   #19  |  Link
Sharktooth
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Thanks. Can you also provide a small clip?
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Old 17th November 2004, 13:08   #20  |  Link
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Sure, i'll post it this evening (i've the encodings on home PC)!
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